Finally finished my first Steampunking of a Nerf Maverick: modified for more power and with cosmetic additions such as a steam exhaust pipe, scope with crosshairs, and steam pressure gauge.
I pulled out nearly every metallic flavor of paint I have and combined different airbrush and hand brushing techniques to give this thing as much detail as possible.

Where to begin? First a basecoat of Krylon Fusion Nickel Shimmer, then I just went to town airbrushing and hand brushing and drybrushing with every metal in the above list.
The entire assembly was then sealed with several coats of Future Floor Polish for semi-gloss shine and durability.